The present invention relates to an expansion valve for controlling the flow rate of a refrigerant supplied to an evaporator in a refrigeration cycle of an air conditioning device, a refrigerating device and the like.
This type of expansion valve is used in a refrigeration cycle of an air conditioning device of a vehicle and the like, wherein FIG. 15 is a vertical cross-sectional view of one example of an expansion valve widely used conventionally shown together with an outline of the refrigeration cycle, and FIG. 16 shows the main portion thereof. The expansion valve 10 includes a roughly prismatic-shaped aluminum valve body 30 comprising a first passage 32 mounted in a refrigerant duct 11 of the refrigeration cycle from a refrigerant exit of a condenser 5 through a receiver 6 to a refrigerant entrance of an evaporator 8 through which a liquid-phase refrigerant travels, and a second passage 34 mounted in the refrigerant duct 11 from a refrigerant exit of the evaporator 8 to a refrigerant entrance of a compressor 4 through which a gas-phase refrigerant travels, said first passage 32 and said second passage 34 positioned above or below one another and separated by a separation wall 38f.
On the first passage 32 is formed an orifice 32a for performing an adiabatic expansion of the liquid refrigerant being supplied from the refrigerant exit of the receiver 6. A valve seat is formed on the entrance side of the orifice 32a or upper stream side of the first passage, and a valve 32b having a spherical shape supported by a valve member 32c from the upper stream side is positioned on said valve seat, wherein the valve 32b and the valve member 32c are fixed together by welding. The valve member 32c is positioned between the valve and a biasing means 32d of a compression spring and the like mounted on the lower portion of the valve body, and transmits the biasing force of the biasing means 32d to the valve 32b. The valve 32b is biased in the direction approaching the valve seat.
The first passage 32 to which the liquid refrigerant from the receiver 6 is introduced works as a passage for the liquid refrigerant, which comprises an entrance port 321 and a valve chamber 35 connected to the entrance port 321. The valve chamber 35 is a chamber with a bottom formed coaxial to the orifice 32a, which is sealed by a plug 39. The valve chamber 35 is communicated to the exit port 322 through the orifice 32a, and the exit port 322 is connected to the refrigerant entrance of the evaporator 8.
Further, the valve body 30 includes a small radius hole 37 and a large radius hole 38 having a larger radius than the hole 37 formed coaxial to the orifice 32a and penetrating the second passage 34, so as to provide a driving force to the valve 32b and to open or close the orifice 32a in correspondence to the exit temperature of the evaporator 8. On the upper end of the valve body 30 is formed a screw hole 361 where a power element portion 36 working as a heat sensing portion is fixed.
The power element portion 36 is a member driven in correspondence to pressure, comprising a diaphragm 36a which is a metallic thin plate made of stainless steel with flexibility, an upper cover 36d and a lower cover 36h made of stainless steel mounted so as to contact each other with the diaphragm 36a positioned therebetween and working as sealing walls each defining a pressure chamber, an upper pressure chamber 36d and a lower pressure chamber 36c, having said diaphragm as one wall surface and divided into the upper and lower chambers by the diaphragm, and a blind plug 36i made of stainless steel for filling a predetermined refrigerant for sensing temperature and working as a diaphragm driving medium into said upper pressure chamber 36b, wherein said lower pressure chamber 36c is communicated to the second passage 34 through a pressure equalization hole 36e formed concentric to the center line of the orifice 32a. A refrigerant steam from the evaporator 8 flows through the second passage 34, and the passage 34 works as a passage for the gas-phase refrigerant, the pressure of said gas-phase refrigerant being loaded to the lower pressure chamber 36c through the pressure equalization hole 36e. Further, a pipe-like mounting seat 362 is formed on the lower cover 36h, the mounting seat 362 being screwed onto the screw hole 361, thereby being fixed to the valve body 30.
The present body further includes a heat sensing shaft 36f made of aluminum, which contacts the diaphragm 36a inside the lower pressure chamber 36c and positioned so as to penetrate the second passage 34 and mounted slidably inside the large radius hole 38 in the separation hole 38f, thereby communicating the refrigerant exit temperature of the evaporator 8 to the lower pressure chamber 36c, and at the same time, provides drive force by being slided inside the large radius hole in correspondence to the displacement of the diaphragm 36a accompanied by the pressure difference between the upper pressure chamber 36b and the lower pressure chamber 36c. The body further includes an operation shaft 37f made of stainless steel positioned slidably inside the small radius hole 37 and having a smaller radius than the heat sensing shaft 36f for pressing the valve 32b against the bias force of the biasing means 32d in correspondence to the displacement of the heat sensing shaft 36f. The heat sensing shaft 36f is equipped with a sealing member for securing the sealing ability between the first passage 32 and the second passage 34, such as an o-ring 36g. An upper end portion 36k of the heat sensing shaft 36f contacts the lower surface of the diaphragm 36a as a receiving portion, and comprises a stopper portion 36L enlarged to the radial direction so as to gain a large contact area with the diaphragm. The displacement of the diaphragm 36a is transmitted to the valve 32b through the heat sensing shaft 36f, and the stopper portion 36L is supported by the lower cover 36h so that the upper end portion 36k of the heat sensing shaft 36f may be slid inside the lower pressure chamber 36c.
Moreover, the lower end of the heat sensing shaft 36f contacts the upper end of the operation shaft 37f at the bottom portion of the large radius hole 38 and the lower end of the operation shaft contacts the valve 32b. The heat sensing shaft 36f together with the operation shaft 37f form a heat sensing drive shaft, and this heat sensing drive shaft acts as a valve drive shaft for transmitting the displacement of the diaphragm 36a to the valve 32b, which comprises of an upper end portion and a heat conducting portion.
In the structure of the power element portion 36, the heat sensing shaft 36f and the operation shaft 37f, when the operation shaft 37f is inserted to the small radius hole 37 and the heat sensing shaft 36f is inserted to the large radius hole 38, the mounting seat 362 on the lower cover 36h is fixed by being connected to a screw hole 361, the seal between the lower cover 36h and the valve body 30 being secured by the o-ring 36m. The screw hole 361 together with the lower cover 36h and the diaphragm 36a form the lower pressure chamber 36c.
Accordingly, on the pressure equalization hole 36e, a valve drive shaft extended from the lower surface of the diaphragm 36a to the orifice 32a of the first passage 32 is concentrically positioned. Further, the portion 37e of the operation shaft 37f is formed smaller (narrower) than the inner radius of the orifice 32a so as to be inserted through the orifice 32a, and thereby, the refrigerant may pass through the orifice 32a.
FIG. 16(A) is a schematic view showing the structure of the power element portion 36 and the heat sensing shaft 36f in the expansion valve 10 explained above, and FIG. 16(B) is a view taken from the direction of the arrow of FIG. 16(A), showing the state where the lower cover 36h is rotated and removed from the screw hole 361, so that the power element portion 36 and the heat sensing shaft are separated. FIG. 16(C) is a vertical cross-sectional view showing the structure of the power element portion 36 and the heat sensing shaft 36f. In the above structure, a predetermined refrigerant for sensing temperature is filled inside the upper pressure chamber 36b of the pressure housing 36d as a diaphragm drive medium (for example, the same gas as the refrigerant gas used in the refrigeration cycle), and the temperature of the refrigerant coming out from the refrigerant exit of the evaporator 8 and flowing through the second passage 34 is transmitted to the diaphragm drive medium through the diaphragm 36a and the heat sensing shaft 36f exposed to the second passage 34 or the pressure equalization hole 36e communicated to the second passage 34.
The diaphragm drive medium inside the upper pressure chamber 36b changes into gas in correspondence to the temperature being transmitted thereto, thereby changing the pressure inside said chamber which is loaded to the upper surface of the diaphragm 36a. The diaphragm 36a is vertically displaced by the difference between the pressure of the diaphragm drive gas loaded to the upper surface thereof and the pressure loaded to the lower surface thereof.
The displacement of the center area of the diaphragm 36a in the vertical direction is transmitted to the valve 32b through the heat sensing drive shaft, and moves the valve 32b close to or away from the valve seat of the orifice 32a. As a result, the flow path area of the orifice 32a is changed, and the flow rate of the refrigerant is controlled.
In other words, the heat sensing shaft 36f positioned inside the second passage 34 connected to the exit side of the evaporator 8 transmits the temperature of the low-pressure gas-phase refrigerant sent out from the evaporator to the upper pressure chamber 36b, and corresponding to the temperature, the pressure inside the upper pressure chamber 36b is changed. When the exit temperature of the evaporator 8 is high or heat load of the evaporator is increased, the pressure inside the upper pressure chamber 36b is raised, and in response, the heat sensing shaft 36f or heat sensing drive shaft is driven to the lower direction so as to lower the valve 32b, thereby increasing the opening of the orifice 32a. Accordingly, the quantity of the refrigerant supplied to the evaporator 8 will be increased, thereby lowering the temperature of the evaporator 8. In contrast, if the temperature of the refrigerant sent out from the evaporator 8 is decreased or heat load of the evaporator is decreased, the valve 32b is driven to the opposite direction, and the opening of the orifice 32a is decreased. Accordingly, the quantity of the refrigerant supplied to the evaporator 8 will be decreased, thereby increasing the temperature of the evaporator 8.
Similar to the expansion valve of the prior art shown in FIG. 15, FIG. 17 shows an expansion valve according to the prior art comprising a valve positioned to oppose to an orifice formed in the middle of a high-pressure refrigerant passage through which a high-pressure refrigerant sent into the evaporator travels, wherein the valve is driven to open or close in correspondence to the temperature of the low-pressure refrigerant sent out from the evaporator.
FIG. 17 is a vertical cross-sectional view showing the prior art expansion valve, and FIG. 18 is a drawing showing the main portion of FIG. 17. In FIG. 17, the same reference numbers as the prior art expansion valve of FIG. 15 show either the same or similar portions, but the structure of the heat sensing drive shaft differs from that shown in FIG. 15. In the expansion valve 101 shown in FIG. 17, the valve body 30 comprises a similar valve body as in the example shown in FIG. 15, and basically comprises an orifice 32a formed in a high-pressure refrigerant passage 32 through which a high-pressure refrigerant to be sent into the evaporator 8 travels, a spherical valve 32b positioned so as to oppose to said orifice 32a from the upper stream side of said refrigerant, a biasing means 32d for biasing said valve toward said orifice from the upper stream side, a valve member 32c positioned between said biasing means and said valve so as to transmit the biasing force of said biasing means to said valve 32b, a power element portion 36 driven in correspondence to the temperature of the low-pressure refrigerant sent out from said evaporator, and a heat sensing drive shaft or rod portion inserted through said orifice comprising a heat sensing shaft and an operation shaft formed integrally and positioned between said power element portion 36 and said valve 32b, wherein said valve could be driven close to or away from said orifice by said rod portion according to the movement of said power element portion, so that the flow rate of the refrigerant passing through the orifice may be controlled.
The heat sensing drive shaft 318 comprises a separately formed upper end portion 36k and an integrally formed heat sensing shaft and operation shaft as, for example, a stainless steel rod portion 316 having a small radius. The upper end portion 36k acts as a receiving portion contacted to the lower surface of the diaphragm 36a, comprising a stopper portion 312 enlarged to the radial direction and a large radius portion 314 whose other end portion forms a protrusion 315 on the center thereof and inserted slidably to the lower pressure chamber 36c. Further, the upper end of the rod portion 316 is connected to the interior of the protrusion 315 on the large radius portion 314, and the lower end thereof contacts the valve 32b.
The rod portion 316 forming the heat sensingshaft is driven vertically traversing the passage 34 in correspondence to the displacement of the diaphragm 36a in the power element portion 36, so a clearance communicating the passage 322 and the passage 34 may be formed along the rod portion 316. In order to prevent such communication, an o-ring 40 contacted to the outer peripheral of the rod portion 316 is positioned inside the large radius hole 38, so that the o-ring exists between the two passages. Moreover, as a detent for preventing the o-ring 40 from moving by the force operating in the longitudinal direction (the direction of the power element portion 36) by the refrigerant pressure of the passage 321 and the coil spring 32d, a washer or snap ring with teeth 41 is positioned inside the large radius hole 38 contacting the o-ring 40 so as to fix the o-ring. The rod portion 316 is formed for example by stainless steel, having a diameter of approximately 2.4 mm, and the portion where the orifice 32a of the rod portion 316 is inserted is formed to have a diameter of approximately 1.6 mm.
In the prior art example shown in FIG. 16, the stopper portion 312 and the large radius portion 314 may be formed of brass, and the rod portion 316 may be formed of aluminum. Further, the stopper portion, the large radius portion and the rod portion may all be formed of stainless steel. In the prior art expansion valve shown in FIG. 18, the displacement of the diaphragm 36a is transmitted by the rod portion 316 to the spherical valve 32b, which moves the valve 32b close to or away from the orifice 32a so as to control the flow rate of the refrigerant, which is similar to the example shown in FIG. 15.
Further, similar to the expansion valve of FIG. 15, the valve shown in FIG. 17 is also filled with a predetermined refrigerant by use of a plug body 36i. The plug body 36i made for example of stainless steel is inserted so as to cover the hole 36j formed on the stainless steel upper cover 36d and fixed thereto by welding.
FIG. 18(A) shows a schematic view of the structure of the power element portion 36 of the expansion valve 101 explained above, and FIG. 18(B) is a view taken from the direction of the arrow of FIG. 18(A), wherein the lower cover 36h is rotated and removed from the screw hole 361, separating the power element portion 36. FIG. 18(C) is a cross-sectional view showing the structure of the power element portion 36.